The present invention relates in general to so-called paper cans, and in particular to a new and useful container with a water-proof structure, which can be used for retort sterilization, after a product is supplied to the container, and its manufacturing method.
Sterilizing of a product in a sealed container by applying hot water or steam to the outside of the container is necessary to preserve the product for a long period. One method in this direction is by use of an aluminum or steel can. However, this involves environmental problems because of disposal of empty cans, whose collection costs a lot of money and labor.
Such being the situation, it is proposed that some other containers should replace metal cans. However, as any replacement must be resistant against heat, water content and pressure because of retort-sterilization, nothing has yet been produced to take the place of metal cans.
Glass containers are also generally used, but they are likely to be broken during transportation, are high in weight and cost, and, like metal cans, involve environmental problems.